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Sponges boom thanks to Antarctic ice shelf bust

Previously thought to grow at a slow pace, the sea creatures exploded in number

Glass sponges provide habitat for feather and brittle stars in frigid Antarctic waters. The creatures (shown here in the western Weddell Sea) made a surprising emergence following the collapse of the Larsen A ice shelf.

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When a catastrophic ice shelf collapse in Antarctica opened up prime ocean real estate, enterprising delicate creatures called glass sponges showed up with unprecedented speed to stake their claim. The finding suggests that even in frigid places, sea life may adapt rapidly to climate change.

Cloaked in darkness and cut off from the photosynthetic power of the sun, the waters beneath Antarctic ice shelves host sparse signs of life. But when a giant shelf collapses — as Larsen A and B did in 1995 and 2002 — solar-powered plankton production ramps up, and scientists think it could jump-start a complex food web of diverse marine life.

A 2007 expedition revealed that sea squirts had taken over the area of the seafloor once shaded by Larsen A. When Claudio Richter, of the Alfred Wegener Institute in Bremerhaven, Germany, and his team went to the same spot in 2011 to see how the squirt coup had progressed, they were shocked at what they found instead.

“The sea squirts were gone, and all of a sudden the glass sponges had tripled,” Richter says.

The discovery, published July 11 in Current Biology, surprised Richter because scientists had previously seen the vase-shaped sponges known as hexactinellids growing at a slow pace, sometimes taking decades to mature. The signals that triggered the sponge boom remain enigmatic.

“This sudden expansion of a glass sponge is unprecedented,” says Paul Dayton of Scripps Institution of Oceanography in La Jolla, Calif. Dayton, who has studied the sponges for decades, sees the boom as a temporary pulse. Other predators will likely take over, he predicts.

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